An emergency brake system such as an advanced emergency brake (AEB) system performs functions such as predicting a collision emergency of a front vehicle (e.g., a vehicle in front of a traveling vehicle), providing a warning, assisting in applying vehicle brakes, and performing an emergency automatic brake. When a subject vehicle continuously drives at a current velocity (vrel), a time-to-collision (TTC) may be calculated using Equation 1 below to predict a collision with the front vehicle based on a distance between the subject vehicle and the front vehicle (c). Warning times related to an emergency brake, the assisting of the braking by the driver, and the like may be determined based on the TTC.
                    TTC        =                  c                      v            rel                                              Equation        ⁢                                  ⁢        1            
The above-mentioned emergency brake system is based on monitoring vehicles that surround the subject vehicle using front, side, and rear radars of the vehicle and a stereo imaging device may be limited in certain situations.
An emergency brake system according to related art may not determine risk of collision with a crossing vehicle (e.g., a vehicle moving in a direction substantially across the subject vehicle), an oncoming vehicle (e.g., a vehicle moving towards the subject vehicle), a rear-ending vehicle (e.g., a vehicle traveling behind the subject vehicle), and the like.